mangafandomcom-20200224-history
HTML5 video
HTML5 video is an element introduced in the HTML5 draft specification for the purpose of playing videos or movies4.8.6 The video element — HTML 5, partially replacing the object element. Adobe Flash Player is widely used to embed video on web sites such as YouTube, since the majority of web browsers have Adobe's Flash Player installed (with exceptions such as the browsers on the Apple iPhone and iPad and on Android 2.1 or less). HTML5 video is intended by its creators to become the new standard way to show video online, but has been hampered by lack of agreement as to which video formats should be supported in the video tag. Example The following HTML5 code fragment will embed a WebM video into a web page. This is fallback text to display if the browser does not support the video element. Supported video formats The current HTML5 draft specification does not specify which video formats browsers should support in the video tag. User agents are free to support any video formats they feel are appropriate. Default video format debate It is desirable to specify at least one video format which all user agents (browsers) should support. The ideal format should: *Have good compression, good image quality, and low decode processor use. *Be royalty-free. *In addition to software decoders, a hardware video decoder should exist for the format, as many embedded processors do not have the performance to decode video. Initially, Ogg Theora was the recommended standard video format in HTML5, because it was not affected by any known patents. But on December 10, 2007, the HTML5 specification was updated, replacing the reference to concrete formats: with a placeholder: }} Although Theora is not affected by known patents, companies such as Apple and (reportedly) Nokia are concerned about unknown patents that might affect it, whose owners might be waiting for a corporation with extensive financial resources to use the format before suing. Formats like H.264 might also be subject to unknown patents in principle, but they have been deployed much more widely and so it is presumed that any patent-holders would have already sued someone. Apple has also opposed requiring Ogg format support in the HTML standard (even as a "should" requirement) on the grounds that some devices might support other formats much more easily, and that HTML has historically not required particular formats for anything. Some web developers criticized the removal of the Ogg formats from the specification. A follow-up discussion also occurred on the W3C questions and answers blog. H.264/MPEG-4 AVC is widely used, and has good speed, compression, hardware decoders, and video quality, but is covered by patents. Except in particular cases, users of H.264 have to pay licensing fees to the MPEG LA, a group of patent-holders including Microsoft and Apple. As a result, it has not been considered as a required default codec. Google's acquisition of On2 resulted in the WebM Project, a royalty-free, open source release of VP8, in a Matroska container with Vorbis audio. It is supported by Google Chrome, Opera Browser and Mozilla Firefox. Browser support Table In cases where decoders are not built into the browser, the format support will be dictated by the multimedia framework of the operating system. Consequently, browser support for multimedia formats are influenced by the problem that DirectShow and QuickTime do not support free formats like Theora by default, whereas GStreamer and Phonon cannot safely support other than free formats by default on the free operating systems that they are intended to run on. Usage , in the wake of Apple iPad launch, a number of high-profile sites have started to serve H.264 HTML5 video instead of Flash for user-agents identifying as iPad. , HTML5 video is not currently as widespread as Flash videos, though recent rollouts of experimental HTML5-based video players from DailyMotion (using Ogg Theora and Vorbis format), YouTube (using the H.264 and WebM formats) and Vimeo (using the H.264 format) suggest that interest in adopting HTML5 video is increasing. According to a YouTube blog post, the tag does not currently meet all the needs of a website like YouTube . The main reasons stated include the lack of a standard format, the absence of an effective and reliable means of delivering the video to the browser, JavaScript unable to display video fullscreen, and content protection issues. Notes References External links * * * * Category:HTML cs:HTML5 video fr:Open Video ko:HTML5 동영상 pl:HTML5 video